The clinical use of the total artificial heart has revealed several serious postoperative sequelae. These sequelae include cerebrovascular accidents, immunosuppression, infection, hemorrhage, coagulopathies and acute renal failure. It is not clear what part the implanted device plays in these clinical observations, in relation to the pathophysiologic changes already present in patients in severe cardiac failure. To clarify some of these relationships, plan to study the immunological responses of calves to cardiopulmonary bypass and implantation of cardiac devices similar to those being used clinically. This study will include twelve calves implanted with the pneumatic total artificial hearts using standard cardiopulmonary bypass, five calves implanted with a left ventricle of a total artificial heart without cardiopulmonary bypass, and five calves which will undergo cardiopulmonary bypass only. These animals will be serially evaluated for immunological responses with tests intended to evaluate major portions of the immune system. Primary humoral response will be evaluated by measuring circulating levels of IgG1, IgG2 and IgM. Separation and differential counts of B and T lymphocytes will also be performed. Circulating levels of total complement and C3a, will be assayed along with measurement of C4a and C5a activation. Bacteriocidal phagocytic assays will be performed with alveolar macrophages and neutrophils and additional assays of neutrophils chemotaxis will be performed. A final portion of the study will include immunologic challenge using sheep red blood cells, BCG, and bovine collagen to assess the integrative ability of the immune system to respond after implantation. With the use of the total artificial heart as either a bridge to cardiac transplantation or as a long-term device, the immunocompetence of recipients becomes critically important. The use of the calf as a model for immune function in patients implanted with cardiac devices will provide valuable information for clinical direction and future research studies.